Subsea seawater filtration and treatment system

Abstract

The present invention provides subsea seawater filtration and treatment system, comprising a filtration assembly ( 1,3 ) for filtering out particles and detritus from the seawater; a first pump ( 5 ) comprising an inlet in fluid communication with the filtration assembly ( 1,3 ) and an outlet; a sulphate removal unit ( 6 ) comprising an inlet in fluid communication with the outlet of the first pump ( 5 ), a first fraction outlet for sulphate depleted seawater and a second fraction outlet for sulphate enriched seawater; at least one second pump ( 7 ) comprising an inlet in fluid communication with the first fraction outlet, and an outlet for the sulphate depleted seawater; wherein the second fraction outlet is in fluid communication with the filtration assembly ( 1,3 ), such that the sulphate enriched seawater may be used for backwashing at least a part of the filtration assembly during use.

1 : A subsea seawater filtration and treatment system, comprising:
 a filtration assembly for filtering out particles and detritus from the seawater;   a first pump comprising an inlet in fluid communication with the filtration assembly and an outlet;   a sulphate removal unit comprising an inlet in fluid communication with the outlet of the first pump, a first fraction outlet for sulphate depleted seawater and a second fraction outlet for sulphate enriched seawater:   at least one second pump comprising an inlet in fluid communication with the first fraction outlet and an outlet for the sulphate depleted seawater;   wherein the first pump and the at least one second pump are driven by a common electric motor; and   wherein the second fraction outlet is in fluid communication with the filtration assembly, such that the sulphate enriched seawater may be used for backwashing at least a part of the filtration assembly during use.   
     
     
         2 : A subsea system according to  claim 1 , wherein the filtration assembly comprises a coarse filtration unit and a fine filtration unit, the coarse filtration unit being arranged upstream of the fine filtration unit, and wherein at least a part of the sulphate enriched seawater from the second fraction outlet is guided to backwash at least a segment of the fine filtration unit during use. 
     
     
         3 : A subsea system according to  claim 1 , wherein the filtration assembly comprises a coarse filtration unit and a fine filtration unit, the coarse filtration unit being arranged upstream of the fine filtration unit, and wherein at least a part of the seawater from the second fraction outlet is guided to assist in backwashing the coarse filtration unit during use. 
     
     
         4 : A subsea system according to  claim 2 , wherein the fine filtration unit comprises multiple filter cartridges and the second fraction outlet is in fluid communication with the fine filtration unit such that the sulphate enriched seawater may backwash at least one filter cartridge during use while the remaining cartridges are in operation. 
     
     
         5 : A subsea system according to  claim 3 , wherein the coarse filtration unit is in fluid communication with the second fraction outlet via an ejector, such that the flow of at least a part of the sulphate enriched seawater is a driving fluid in the ejector to provide suction for backwashing the coarse filtration unit during use. 
     
     
         6 : A subsea system according to  claim 1 , wherein the second fraction outlet is in fluid communication with a subsea cooling assembly. 
     
     
         7 : A subsea system according to  claim 6 , wherein the cooling assembly is connected to at least one of a motor and a variable speed drive/transformer. 
     
     
         8 : A subsea system according to  claim 6 , wherein the cooling assembly is connected to a process fluid heat exchanger. 
     
     
         9 : A method for subsea filtering and treatment of seawater, comprising the steps of:
 filtering the seawater through a filtration assembly;   removing sulphate from the seawater using a sulphate removal unit;   to thereby obtain a first fraction of sulphate depleted seawater and a second fraction of sulphate enriched seawater; and   backwashing the filtration assembly using at least a part of the second fraction of seawater.   
     
     
         10 : A method according to  claim 9 , further comprising the step of using at least a part of the second fraction of sulphate enriched seawater to provide cooling to a subsea cooling assembly. 
     
     
         11 : A method according to  claim 10 , wherein the cooling assembly is connected to at least one of motor, a variable speed drive/transformer, and a process fluid heat exchanger.